List blob containers with .NET

  • Article

When you list the containers in an Azure Storage account from your code, you can specify a number of options to manage how results are returned from Azure Storage. This article shows how to list containers using the Azure Storage client library for .NET.

Prerequisites

Set up your environment

If you don't have an existing project, this section shows you how to set up a project to work with the Azure Blob Storage client library for .NET. The steps include package installation, adding using directives, and creating an authorized client object. For details, see Get started with Azure Blob Storage and .NET.

Install packages

From your project directory, install packages for the Azure Blob Storage and Azure Identity client libraries using the dotnet add package command. The Azure.Identity package is needed for passwordless connections to Azure services.

dotnet add package Azure.Storage.Blobs
dotnet add package Azure.Identity

Add using directives

Add these using directives to the top of your code file:

using Azure.Identity;
using Azure.Storage.Blobs;
using Azure.Storage.Blobs.Models;
using Azure.Storage.Blobs.Specialized;

Some code examples in this article might require additional using directives.

Create a client object

To connect an app to Blob Storage, create an instance of BlobServiceClient. The following example shows how to create a client object using DefaultAzureCredential for authorization:

public BlobServiceClient GetBlobServiceClient(string accountName)
{
    BlobServiceClient client = new(
        new Uri($"https://{accountName}.blob.core.chinacloudapi.cn"),
        new DefaultAzureCredential());

    return client;
}

You can register a service client for dependency injection in a .NET app.

You can also create client objects for specific containers or blobs. To learn more about creating and managing client objects, see Create and manage client objects that interact with data resources.

Authorization

The authorization mechanism must have the necessary permissions to list blob containers. For authorization with Microsoft Entra ID (recommended), you need Azure RBAC built-in role Storage Blob Data Contributor or higher. To learn more, see the authorization guidance for List Containers (REST API).

About container listing options

When listing containers from your code, you can specify options to manage how results are returned from Azure Storage. You can specify the number of results to return in each set of results, and then retrieve the subsequent sets. You can also filter the results by a prefix, and return container metadata with the results. These options are described in the following sections.

To list containers in your storage account, call one of the following methods:

These methods return a list of BlobContainerItem objects. Containers are ordered lexicographically by name.

Manage how many results are returned

By default, a listing operation returns up to 5000 results at a time, but you can specify the number of results that you want each listing operation to return. The examples presented in this article show you how to return results in pages. To learn more about pagination concepts, see Pagination with the Azure SDK for .NET.

Filter results with a prefix

To filter the list of containers, specify a string for the prefix parameter. The prefix string can include one or more characters. Azure Storage then returns only the containers whose names start with that prefix.

Include container metadata

To include container metadata with the results, specify the Metadata value for the BlobContainerTraits enum. Azure Storage includes metadata with each container returned, so you don't need to fetch the container metadata separately.

Include deleted containers

To include soft-deleted containers with the results, specify the Deleted value for the BlobContainerStates enum.

Code example: List containers

The following example asynchronously lists the containers in a storage account that begin with a specified prefix. The example lists containers that begin with the specified prefix and returns the specified number of results per call to the listing operation. It then uses the continuation token to get the next segment of results. The example also returns container metadata with the results.

async static Task ListContainers(BlobServiceClient blobServiceClient, 
                                string prefix, 
                                int? segmentSize)
{
    try
    {
        // Call the listing operation and enumerate the result segment.
        var resultSegment = 
            blobServiceClient.GetBlobContainersAsync(BlobContainerTraits.Metadata, prefix, default)
            .AsPages(default, segmentSize);

        await foreach (Azure.Page<BlobContainerItem> containerPage in resultSegment)
        {
            foreach (BlobContainerItem containerItem in containerPage.Values)
            {
                Console.WriteLine("Container name: {0}", containerItem.Name);
            }

            Console.WriteLine();
        }
    }
    catch (RequestFailedException e)
    {
        Console.WriteLine(e.Message);
        Console.ReadLine();
        throw;
    }
}

Resources

To learn more about listing containers using the Azure Blob Storage client library for .NET, see the following resources.

REST API operations

The Azure SDK for .NET contains libraries that build on top of the Azure REST API, allowing you to interact with REST API operations through familiar .NET paradigms. The client library methods for listing containers use the following REST API operation:

Client library resources

See also

Related content

  • This article is part of the Blob Storage developer guide for .NET. To learn more, see the full list of developer guide articles at Build your .NET app.